This invention relates to a device useful in cutting tubes or pipes in locations that make it impossible to cut the pipe from the outside. At times, it is necessary to remove tubes from boilers, reactors, etc. where the only available access to the tube is at one end of the boiler reactor, etc. and this access is limited to the interior of the tube diameter.
Prior art devices have included various types of cutting devices which at times have had performance limitations which caused problems in obtaining the desired result.
The cutting device must be insertable into the interior of the tube from the end thereof, and must be able to reach the desired cutting location which may be a substantial distance from the end of the boiler or reactor from which the cutter has been inserted.
The cutter will preferably not produce any shavings or other particles of a nature that might be produced by grinding, filing or otherwise abrading the pipe undergoing cutting.
Similarly, the device must not permanently distort the tube undergoing cutting or produce any deflections of a permanent nature in the tube which would impair its future use.
The cutting device must be easy to insert into the tube, and be actuable from the end of the reactor or boiler to produce an acceptable separation of the tube, and the cutting device must be capable of being retracted from the tube when the cutting operation is complete.
Prior art devices have included devices which carry a single or a pair of oppositely disposed cutter wheels mounted in a rotating head of a cutting device.
Such a cutting device is driven by a hollow shaft to produce rotation of the head, and a second co-axial shaft is provided within the hollow shaft which is connected to ramping surfaces associated with the cutter wheels so that translation of the co-axial shaft causes the ramping surfaces to move the cutter wheels into engagement with the pipe and perform the desired operation. This device tends to distort the tube undergoing the cutting operation so that the metallurgical properties of the tube may have been altered in the region where the cutting operation has taken place.
A good example of a prior art inside pipe and tube cutter may be found in U.S. Pat. No. 2,814,105 to Smith. This patent describes a pipe cutting device having two oppositely disposed cutting wheels, which are adjustable in a radial direction to produce a rotary cut inside a pipe. The device is intended to be used for producing cuts in pipes at a location near the end of the pipe.
Because the device is intended to cut cast iron soil pipes, the axes of the cutting device need not be stabilized in the pipe at the lower end, thus, the cutter wheels may cause the axis of the device to nutate, and if the device is employed for severing ductile pipe, the distoration of the pipe during the severing operation may not be acceptable.
U.S. Pat. No. 4,424,629 to Schott shows a very complex device useful in severing boiler tubes from the inside of the tube. The device is centered in the tube by a pair of eccentric guide rolls and a single hydraulically actuated cutter wheel is advanced to cut the tube during rotation of the tool.
The distortion produced by this device cannot be overemphasized, and the complexity of the device is sufficient to make the device uneconomical to manufacture. The limit of travel allowed for the cutting wheel confines the use of this device to a small range of pipes or tubes.